const ctx = canvas.getContext('2d'); let img = canvas.createImage(); img.src = imgUrl; img.onload = (e) => { ctx.drawImage(img, 0, 0, 60, 60); wx.canvasGetImageData({ canvasId: canvasId,  x: 0,  y: 0,  width: 60,  height: 60, fail(e){ // 输出canvas内容是 empty， 要如何获取imageData } }) };